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2020 Eugene Wastewater Master Plan Chapter 3: Existing Wastewater Systems 8 Chapter 3 - Existing Wastewater Systems PURPOSE The purpose of this chapter is to provide detailed information about Eugene’s seven major wastewater basins and evaluate the wastewater system infrastructure, including pipe and pump stations, to provide adequate service to meet current and future needs. The main sections in this chapter discuss historical background, major basins, system characteristics, and existing pump and lift stations. HISTORICAL BACKGROUND Wastewater construction began in central Eugene between 1900 and 1910. The wastewater collection system expanded very slowly prior to 1945. The initial system was a combined storm and wastewater system. After World War II, the Eugene system expanded rapidly to provide service to development in newly annexed areas. Development was also rapid in areas outside the city (Willakenzie, Bethel-Danebo, River Road, and Santa Clara) where wastewater service was initially provided by individual septic tanks. The combined wastewater system discharged untreated wastes to the Willamette River until about 1950 when the first Eugene primary wastewater treatment plant was constructed at the present River Avenue site. Major treatment plant improvements were made in 1959, 1965, and 1970 to increase capacity and upgrade from primary to secondary treatment. A major wastewater rehabilitation program was also accomplished between 1960 and 1970. The combined storm and wastewater system in the older central Eugene area caused serious overloads in the collection system and also at the treatment plant. Separate wastewater pipes were constructed and most of the direct stormwater inflow from street and alley drainage was removed from the wastewater system. Construction costs for separation of the combined system totaled about $6 million. This would be equivalent to about $70 million in 2019 dollars. In 1977, Eugene, Springfield, and Lane County jointly formed the Metropolitan Wastewater Management Commission (MWMC) to develop a regional wastewater treatment system for the Eugene-Springfield Metropolitan Service Area. The Eugene treatment plant on River Avenue was enlarged to accommodate the new regional wastewater flows. The new plant was completed in 1984 and serves the entire Eugene- Springfield area. At that time, it was designed to process a peak wet weather flow of 175 MGD. Between 1980 and 1999 major collection system expansion occurred. Approximately 32 percent of the current system was built in that time frame. Interceptors, pump stations, and pressure lines were constructed to serve the River Road, Santa Clara, and west Eugene/Willow Creek areas. In the late 1990s, a wastewater model for the Eugene-Springfield service area was developed by CH2MHill. The primary focus of that model was to support the regional wastewater treatment plant improvements. That model, and subsequent updates, focused on large-diameter pipes, typically 12 inches in diameter and greater. In 2014, the City of Eugene’s staff began working on a Eugene model. All pipes with diameters 10 inches and larger and all connected pump stations were included in the model. In 2016 the model was fully calibrated for both wet weather and dry weather flows and work began to